Pressure regulating and selecting system for aircraft instruments



June 9, 1953 s. M. CLIPPINGER 2,641,274 yPRESSURE! REGULATING AND SEL ING SYSTEM FOR AIRCR INSTRU TS Fileq Feb.

. INVENTOR .Sfw/mr M CL /PP//VGE/e Patented June 9, 1953 PRESSUREv REGULATINGY AND SELECTING SYSTEM-1 FOB@ AlRCRAFT- INSTRUMENTS Stewart Clippinger, East Orange, N. J.,/as

signorl to'A The Sperry Corporation, a corporation of Delaware Application February 2 6, 194,7,l Serial No. 731,1341

4Claimsy. l

This inventionv relatesto pressure regulatingv and selectingsystems arnihasvl reference more particularly to a novel valve device .y forl aut/0.: matioally selecting andY maintaining constant the pressure to instrurnent-or,` instruments from one of aplurality oi'pressure'sources.

At present, pneumatioairorait instruments are operated from various sources orf-air pressure. These sources are generally of three forms; a Venturi tuba a hleed tromy the intake, manifold of the aircrafts power. plant, or` a pneumatic pump connectedA to and driven by the power plant of the aircraft. Usually a vacuum or negative pressure system is employed'although Athe valve of the present invention is applicableto positive pressures or pressures abovethat of at-` mosphere. The usual practice in supplying this pressure to an instrument has beenrst through a selector valve which is manually operated and` selects the pressure from any one ofthe pres,- sure sources. Between the selector val-ve and the instrument, there isgenerally placeda vacuum regulator. to maintain the pressure inv-the instrument at a predetermined value.

The usually employed system has-several; dis,- advantages. In. the event of icing conditions, a Venturi tube may become uselessl and theplDt ust remember to throw the selector valve, from venturi to manifoldf for example, asV soon as these icing conditions are discernible.Y Ify he fails to do this, the instrument by which he is iiying will slowdown and, if such instrument is of the gyroscopio type, procession will occur, thereby giving an erroneous indication of the aircrats attitude, in the Venturi position and with `a pilot chang-` ing from cruising speed to a glide as in approaching an airport, the resulting pressure drop at the venturi would cause a corresponding. error in instrument indication and the pilot must again remember to throw the manual selector switch from venturi to manifold Another disadvantage ofn the system, as usually employed, is that upon the failure of a pilot tov move the manually operated selectorI valve to the Venturi position prior to theopeningiof the throttle for take-off, a-verylow'orpractically zero pressure in the manifoldvresultsin a like pressure at the instrument, causing an erroneous indication of the instrument.

By my present invention, i have overcome all of these disadvantages. My apparatus auton matically selects that sou-roe of pressure which is high enough' for the reg-ulatortol maintain the It is a function of this regulator Also, with the. selector valve pressure at the instrument at a predetermined value. For example, if the pilot is ying under icing conditions and his venturi ices up and becomesv useless, my device will automatically out out the. Venturi pressure source and open the intake, manifold pressure source; or if the device is used in aircraft in which pressure pumps are used,v if the vmotor which is supplyingl the instrument with pressure fails, my device will automatically shift the flow of pressure from the instrument tothel vacuum pump on one of the other ofthe motors.

Therefore, it is the principal object of my invention to provide in a system for driving a plurality of pneumatically operated aircraft instruments from a plurality of pneumatic pressureV sources means for connecting the conduit from said instruments to the conduits oi said pressure sources whereby upon failure of the normally connected source of pressure to supply sunicient pressure to said instruments another of said sources will be automatically connected to said instrumentconduit.

' Another. object of my invention is to provide in a system'of the` above character a novel, unitary device irnzluding pneumatically operated valve means for connecting said instrument conduit to one1 of said pressure source conduits when the pressure of theother of said source conduits falls below a predetermined Value.

further object of my invention is to provide in a `system of the',y alcove character a novel unitary,v devic'eincluding valve means for connecting said instrument conduit to one oi said pressure'sourceoonduits when the pressure of the other of said sources fallshelow a predetermined value and means for eiiectively closing the conduit to this deiicient source.

' still yfurther object of my invention is to provide ina system oi the above character means for maintaining the pressure at said instruments ata constant predetermined pressure value.

Throughout the specication, the term pressure.l is used. I use this term in` a broad sense to includesuperatniospheric pressure or underatmospheric pressure known as vacuum the latter being4 the system most generally used in connectionwith aircraft instruments, and being theftypespecially described herein.

Other ohiectsl and advantages will become apparent'irom the specication taken in connection with thev accompanying drawings, wherein,

Fig-l is aclsgram showing the system oi the present; invention employing aplurality oi instruments, a Venturi tube providing one source of vacuum pressure and a manifold bleed Droviding the other source of vacuum pressure and their respective connecting conduits;

Fig. 2 is a longitudinal, sectional view of the device with the valves and associated elements in a position whereby the pressure at the Venturi tube is employed;

Fig. 3 is a view similar to Fig. 2 with the various elements of the device in a position for supplying pressure to the instruments from the manifold of the aircrafts engine when the pressure at the venturi falls below a predetermined value; and

Fig. 4 is a sectional View taken on line 4-4 of Fig. 2.

Referring now to Fig. l, there are shown two pressure-producing means which are, in the ernbodiment illustrated, productive of pressures below that of atmosphere, one of the means schematically represented as a Venturi tube It and the other the manifold of the aircrafts motor I I. A plurality of pneumatically operated aircraft instruments are shown as driven by these selective pressure sources, which instruments include an artificial horizon I2, a directional gyroscope I3 and a bank and turn indicator i4. However, it will be understood that the valve illustrated is equally adaptable to any apparatus which utilizes fluid pressure. Between the pressure sources I and II and the instruments I2, I3 and I4, there is shown my novel selecting and regulating device I5 and a plurality of conduits for connecting the various elements of the system. Conduit I5 connects the device I5 and venturi i, conduit Il connects the device I5 and the manifold of the engine II, and conduits I8, I9 and 2U connect the instruments to the device l5 through a common conduit 2I. Each instrument is provided with a filter member 22 so that all air flowing from the instruments to the vacuum sources ECI and II must pass through these filters, whereby no unfiltered air may pass to the manifold of the aircraft engine without rst being cleaned of all foreign particles, such as dust and the like.

Fig. 2 shows in more detail the device I5 of the present invention. It consists mainly of a body portion or housing 23 with its various communieating bores having connections between the conduits I6, I'I and 2I. The housing 23 has a central interior chamber 24 therein which is common to all three conduits It, I1 and 2| through lateral connecting passages 25, 28 and 21. The housing 23 is also provided with two end cavities each having a diaphragm 28, 29 which divides each of said end cavities into two chambers 3|, 32 and 33, 34.

Chambers 3l and 34 are formed by recessed end plates 30, 30 which serve to hold diaphragms 28 and 29 in position and are provided with openings 40, which subject chambers 3I and 34 to the pressure of atmosphere. Chambers 32 and 33 are separated from central interior chamber 24 by end washers 35 and 36 and are subject to the pressures in conduits 2l and I5, respectively, to be described more fully as the description proceeds. v

The central interior chamber 24 has movably mounted therein a pair of balance piston valves 31 and 38. Each valve has a number of longitudinal holes 39 drilled therethrough. These holes allow the pressure within chamber 24 to be distributed evenly on each face of the valve so that there will be no differential pressure in the chamber 24 which will impede the movement of the valves within the said chamber.

Piston valve 3l has a projecting rod or arm 4I which ts movably through a hole in end Washer 35 and is fastened at its end portion to the diaphragm 28 so that movement of the diaphragm will cause a similar movement of the rod and valve. Also connected to the end of rod 4I is a rigid plate 42, Plate 42 serves as a seat for one end of a spring 43, the other end of which is seated in an annular groove 44 in housing 23. The movement of valve 3l and its associated parts is controlled by a passage 45 connecting Y the lateral passage 2'! of instrument conduit 2| to the chamber 32. Its function will be explained fully in the description of the operation.

The piston valve 38 has a similar construction to that of valve 31. Arm 43, which is integral with valve 38, fits movably through end washer 35 and has its end portion fastened to the diaphragm 29 and is movable therewith. The end portion of rod 4E also has fastened thereto a rigid plate 4'! which serves as a seat for one end of spring v4.8. The other end of the spring 48 is seated in an annular groove 49 in the casing 23. The movement of valve 38 and its associated parts is controlled by a passage 5I which connects lateral passage 25 of pressure source conduit I6. Its function will also be explained fully in the following description of the operation.

Located in the lateral passage 25 is a check valve 52 which seats itself upon a flat surface provided by the lessened diameter of lateral passage 25 near the central interior chamber 24. The check valve 52 serves to open or close the conduit i6 to the interior chamber 24. A similar check valve 53 is provided in lateral passage 26 in a similar manner as check valve 52. As mentioned above, at take-olf the pressure at the intake manifold drops to zero and a vacuum is created at the venturi, but this vacuum pressure is insufficient to overcome the pressure of spring 43 and both piston valves are momentarily open. Check valve 53 serves to prevent the gas mixture in the intake manifold from passing to the venturi through interior chamber 24 thereby avoiding a dangerous nre hazard. It is desirable to pivotally mount these check valves loosely on a pin so that they are slightly movable and each can find its own best seating position.

The operation of the device of my invention will now be described. In normal flight in clear weather, the position of the valves and their associated elements are in the position shown in Fig. 2 with the Venturi tube as the principal or normal source of pressure. The venturi IU draws air `under pressure from the atmosphere through filters 22 of the instruments I2, t3 and I4 driving their respective rotors and indicating mechanism. This air under pressure flows through conduits i8, I3 and 20 and into common instrument conduit 2I and thence into lateral passage 2l. From passage 2 it flows into the central interior chamber 24 where the negative pressure is distributed throughout the chamber by means of holes 39 in the valves 3T and 38, thereby allowing the valves to float, that is, to have no differential pressures on their faces.

rhe Venturi pressure then draws the air into lateral passage 25 and maintains the check valve 1n an open position and the air is also drawn from lateral passage 25 into source conduit I 6 and thence to venturi I. The venturi also draws air from the end chamber 33, thus creating a differential air pressure on each side of diaphragm 29, the chamber 34 being subject to atmospheric air pressure through openings 40. The pressure in chamber 33, being less than that in chamber 34, causes the diaphragm 29 to move to the left acapara;

sition.-

Letfusassume that -the'aircraft which has been iiying in- Y clear4 weather.;4 as described f above, and` the pneumatic Jflight instruments 4have been operated bye pressure created bythe `Venturi tube,y nowv strikes bad-weather; thevis-ibilityldrops vto. zero Yand `ice begins toformf on the craft; The' pilot-must now iiygby instrumentsalone, but the icing `conditions -l havedisabled theV Venturi tube therefore, the 4pressure must now bederived -gfrom` another-source, .fory exam-ple the` crafts enginer manifold.

This change is accomplished ,automatically by4 my'vdevice as --follows;1 The-ventur-, which -has' been creating the vacuum pressurefortheinstruments,now is useless and air at atmospheric pressure appears in-source conduit IB and-inlateral passage 25.* The air,` intrying `to -iiow backinto the instruments I2,4 Ii-'Sand I4 through central in terior chamber 24 to bring the system to an equal pressurecondition, closes check valve 52 which arrests ythis backward now However, the atmospheric pressure does appear in passage 5I and therefore in end chamber 33: Sincethere isnow air under atmospheric.fpressureon .each side of diaphragm 29, the only pressureon the diaphragm will bethat created by the springfl which forces diaphragmrZS throughspringseat lil to the right. The pistonrvalve 38, being xedly attached to diaphragm 45, also moves to theright thereby opening theiateral passage 25. The opening oipassage 26 permits the pressure created in the engine manifold to drive the instruments I2, I3 and I4 through instrument conduit 2l, central interior chamber 24 and source conduit I'I.

If the aircraft now nies into clear weather again and the ice disappears from the venturi, the vacuum pressure created thereby appears in source conduit I6, lateral passage 25 and thus in end chamber 33 through passage 5I, creating a differential pressure on diaphragm 29 and causing piston valve 38 to move to the left closing source conduit I1. Check Valve 52 will Open and permit air to flow from instruments I2, I 3 and I4 through instrument conduit 2I into interior chamber 24 and thence to source conduit II to venturi I0.

It will be understood that this selection will take place at any time when the pressure created by the Venturi source is not suicient to drive the instruments at ful-l speed, as described above.

Another feature of my invention is to provide an automatic regulator in the same small compact housing 23 which contains the pressure source selector. In describing this feature let us assume the following conditions: the venturi creates a vacuum pressure of six inches of mercury, the engine manifold a pressure of say ten inches of mercury, and that the instruments are designed to operate at a pressure of four inches of mercury. It is therefore necessary to maintain a constant pressure at the instrument from a variable pressure at the sources.

Neglecting the small pressure drop in the conduits between the instrument and lateral passage 21, there is to be maintained therein a vacuum pressure of four inches of mercury. The instrument pressure appears in end chamber 32 through passage 45 and creates a differential pressure on the diaphragm 28, which pressure is just balanced by the force of the spring 43 thereby maintaining the piston valve 31 in a balanced condition.

Valve-.31 :controls.thegowlofeair.between lateral.v passage21and interiory chamber 2.4 IfV the pres: sure rinchamber Zfis at fVenturipressure of fsXt.v

inches of mercury valve 3l p partially closes.v lat'-` eral passagefZ'I 'causing a drop in pressuretherein;v If the pressure in passage 2l ,r

to fourinches: drops below four inches of mercury, this dropwill appear :in end chamber 32.1.resulting in' a change inthe differential,pressureton diaphragm 23;`

Thetspring t3; responding to. this change, forces diaphragm. 1 28 i to the left which causes :a Scorre,- spondingmovementgof valve'l toitheleft, open-` ingflateral passageZ's'fto thegreater pressurevin interiorchamber 24.n AsthisA greater` pressure.y then appears in -end chamber 32; the valves? will' respond/through actionY of diaphragm .23to restorethe valve'SI vtoits original position allowing. a pressure of four inches of mercury to be'maintained in passage 2'I and instrumentsl, I3 and If ther-automatic selector changes from thev Venturi pressure-source-to the manifold pressure source, a greater pressure will appear in interior chamber-lA 24.'y and in lateral passage 2l; This y greater pressure willvalso appear in end chamber description or shown inthe vaccompanying draw.`

ings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. In an automatic pressure selecting and regulating system, a device adapted to be connected between at least two sources of fluid pressure and a pressure utilizing apparatus, said device comprising, a unitary body portion having a longitudinal internal chamber, Iirst and second ports communicating with said chamber and adapted to be respectively connected to said sources, a third port communicating with said chamber and adapted to be :connected with said apparatus, Valve means responsive to the pressure at said first port for closing said rst port when the pressure therein drops below a predetermined value, diaphragm means having a rst side and a second side, said diaphragm means being responsive to pressure differentials between said iirst and second sides, said rst side being subjected to atmospheric pressure and said second side being subjected to the pressure at said first port, and a balanced piston valve operatively connected directly to said diaphragm means, said piston valve being slidably disposed within said chamber and movable in cooperable relation to said second port, whereby said diaphragm means directly moves said piston valve automatically to open said second port when the pressure at said first port is above a predetermined value and to close said second port when the pressure at said rst port is below said predetermined value.

2. In a unitary valve structure for controlling the flow of a-iiuid operating medium to a pressure-responsive apparatus from at least two sources of uid pressure, a valve body portion having a rst port adapted to be connected to the rst of said sources of pressure, a second port adapted to be connected to the second 0f said sources of pressure, a service port communicable with said first and second ports and adapted to be connected with said apparatus, a check valve element adapted to open and close said first port,

means including pressure responsive-means diff ferentially responsive to the pressure of atmosphere and the pressure at said first port, and a piston valve element operatively connected directly to said pressure responsive means, said piston valve element being slidably disposed in said valve body portion and adapted to open and close said second port, whereby said pressure responsive means directly positions said piston valve element normally to maintain said second port closed and to open said second port only when the pressure of said rst source exceeds a predetermined value.

3. In an automatic pressure selecting and regulating system, a device adapted to be connected between rst and second sources of fluid pressure and a pressure utilizing apparatus, said device comprising a unitary body portion having a longitudinal internal chamber, first and second ports communicating with said chamber and adapted to be respectively connected with said pressure sources, a third port communicating with said internal chamber and adapted to be connected with said apparatus, a first balanced piston valve, a second balanced piston valve, said first valve being in cooperable relation to said rst port, said second valve being in cooperable relation to said second port, both of said valves being slidably disposed in said longitudinal internal chamber and movable independently of each other, a third normally open valve element responsive te the pressure at said first port for cutting out the first source of pressure when the pressure thereat drops below a predetermined value, rst diaphragm means adapted to operate said iirst `piston valve, one side thereof being subjected to atmospheric pressure and the other side being connected to the pressure at said third port, said iirst valve being actuable to partially close said third port when the degree of pressure thereat is above a predetermined value, and to effect a further opening of said port when the Ipressure thereat decreases below a predetermined value, second diaphragm means adapted to operate said second piston valve, one side thereof being subjected to atmospheric pressure and the other side being connected to the pressure at said iirst port, said second valve being actuable to close said second port when said third valve element is open and to effect an opening of said second port when said third valve element is closed.

4. The device recited in claim 3 wherein the iirst diaphragm means is connected directly to the rst piston valve and the second diaphragm means is connected directly to the second piston valve.

STEWART M. CLIPPINGER.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 459,545 Freeman Sept. 15, 1891 2,059,104 Harrah Oct. 27, 1936 2,138,989 Thomas Dec. 6, 1938 2,318,261 St. Clair May 4, 1943 2,509,504. Jensen May 30, 1950 

